Conventional technology associated with valves includes a proposal for a cover for a handle of a valve to “prevent wrong operation of a handle of a valve included in the parts of machinery and equipment” (see patent document 1).
Patent document 1 discloses a valve handle cover whose general features are clearly understood from the figures thereof. Specifically, a valve handle cover 2 is in the shape of a box in which a handle 1 of a valve is completely contained. The box-shaped cover is divided into halves along the diameter of the valve. The first half of the cover is fastened to the second halve thereof with a hinge that is placed so as to contact the respective sidewalls of the first and second halves with its shaft on the cutting line. The box-shaped cover is opened and closed by pivoting the halves around the hinge shaft. The halves are pivoted away from each other around the hinge and thus the box is opened. The handle is inserted into the box from the created opening. Then the cover is closed, with the handle therein, by pivoting the halves back until they meet. As a result, the handle is housed in the handle cover 2. Each of the halves is provided with a small projecting plate that has a keyhole. The cover is locked up with a bolt inserted into the keyholes.
Thus the handle is housed in the valve handle cover 2, which permits only people in charge to operate the valve. In other words, the valve is not easily accessible to an unspecified large number of people; even if they try to operate the valve handle by grasping the handle cover with hands, it is impossible for them to move the handle with all their strength. The valve handle cover disclosed in patent document 1 is technically advantageous in this respect. (See paragraphs [0007], [0008], [0011], and [0013], and FIGS. 1 and 2 of patent document 1.) [0004]
The left and right halves of the valve handle cover disclosed in patent document 1 have to be turned around the hinge so as to be parted away from each other, when the operator places the valve in the cover. As a result, the valve handle cover requires a large space expanding perpendicularly to the axis of the valve. Therefore a technical problem of this device is that the valve handle cover cannot be fitted to the valve unless a sufficiently large space is saved around the valve.
Patent document 2 discloses a device for locking a fluid channel opening/closing handle, “comprising a stopper support (12, 22) secured to a main part (5) of a fluid controller, the stopper support having a through hole (19, 23) which tightly receives a main part (5) of a fluid controller; and a stopper (16, 26) non-rotatably mounted on the stopper support (12, 22) and engaged with the fluid channel opening/closing handle (8) to prevent the handle (8) from rotating” (see claim 1 of patent document 2).
The locking device disclosed in patent document 2 is a device for locking the fluid channel opening/closing handle (8) at a position where the valve is fully opened and at a position where the valve is completely closed (see claim 1 of patent document 2). The device has a structure to actively prevent the rotation of the handle.
Patent document 3 discloses a rotary valve, comprising a locking mechanism that enables the valve to keep a fixed degree of opening. The locking makes it possible to prevent erroneous operation. The locking device does not interfere with rotation of the handwheel when the valve is located in a small space. When the user desires to change a valve with no lock mechanism to the same valve with the lock mechanism, and vice versa, they are just required to change handwheels, which means that the valve itself is continuously used regardless of whether or not the locking mechanism is attached to the handwheel. The locking mechanism ensures that the rotary valve is set to the exact position and kept there unmovably, when the fluid channel is opened and closed and when the communicating channel is switched from one fluid channel to another fluid channel. (See paragraph [0001] of patent document 3.)
Patent document 3 discloses a mechanism to make not rotatable the stem of the valve body, or the rotating shaft.
Patent document 4 discloses “a fluid controller including a stopper (26), which comprises a portion (31) for preventing rotation of the handle when it is located at a position where the valve is fully open and a portion (32) for preventing rotation of the handle when it is located at a position where the valve is completely closed” (see claim 1 of patent document 4). The disclosed fluid controller has structures for preventing rotation of the handle when the handle is located at a position where the valve is fully open and at a position where the valve is completely closed.
Patent document 5 discloses a lock device for a valve comprising a guide tube fixed to the handwheel of the stem of the valve and so arranged that the guide tube rotates together with the handwheel in an integrated manner; a locking bar slidably inserted into the inside of the guide tube wherein a lower end of the locking bar projects from a lower opening of the guide tube; and a strike plate for engaging with the locking bar when the locking bar is lowered. The technical idea of this lock device is to actively control the rotation of the rotating stem so that the rotating stem will not move.
Patent document 6 discloses a device for preventing erroneous operation (11), comprising a cover support (12) secured to the main body 2 of a fluid controller; a tubular handle cover (13) supported on the cover support, the tubular handle cover covering a handle (3) for opening and closing a fluid channel; and coupling means (14) for detachably coupling the tubular handle cover (13) to the cover support (12). The device for preventing erroneous operation (11) has a structure that prevents the handle (3) for opening and closing a fluid channel from being turned unless a lock (24) is opened with a key.
Patent document 7 discloses “a lock device for locking a handle (8) for opening and closing a fluid channel at a position where the fluid channel is fully opened or at a position where the fluid channel is completely closed, the handle rotatable in relation to a main body (5) of a fluid controller, the lock device comprising a stopper support (12) (22) secured to the main body (5), the stopper support having a through hole (19) (23) for receiving the main body; and a stopper (16) (26) fixed to the stopper support (12) (22) in such a manner that the stopper is non-rotatable in relation to the main body and is capable of engaging with the handle (8), thereby preventing rotation of the handle.” (See claim 1 of patent document 7.)
All of the devices disclosed in patent documents 1-7 have a mechanism to prevent rotation of the rotating shaft of the handle for opening and closing a fluid channel.